题目内容
下面各题怎样简便就怎样计算 9.9×25 | 3.25×4.7-7.8 | 1.25×32×0.25 | 8.12×4+1.88×4. |
解:(1)9.9×25,
=(10-0.1)×25,
=250-2.5,
=247.5;
(2)3.25×4.7-7.8,
=15.275-7.8,
=7.475;
(3)1.25×32×0.25,
=1.25×8×4×0.25,
=(1.25×8)×(4×0.25),
=10×1,
=10;
(4)8.12×4+1.88×4,
=(8.12+1.88)×4,
=10×4,
=40.
分析:(1)把9.9看作(10-0.1),运用乘法分配律简算;
(2)先算乘法,再算减法;
(3)把32看作8×4,运用乘法结合律简算;
(4)运用乘法分配律简算.
点评:此题考查了小数的四则混合运算,注意运算顺序,灵活运用所学的运算定律进行简便计算.
=(10-0.1)×25,
=250-2.5,
=247.5;
(2)3.25×4.7-7.8,
=15.275-7.8,
=7.475;
(3)1.25×32×0.25,
=1.25×8×4×0.25,
=(1.25×8)×(4×0.25),
=10×1,
=10;
(4)8.12×4+1.88×4,
=(8.12+1.88)×4,
=10×4,
=40.
分析:(1)把9.9看作(10-0.1),运用乘法分配律简算;
(2)先算乘法,再算减法;
(3)把32看作8×4,运用乘法结合律简算;
(4)运用乘法分配律简算.
点评:此题考查了小数的四则混合运算,注意运算顺序,灵活运用所学的运算定律进行简便计算.
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